Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$173.49	4.842%	$181.8904	$181.89	$181.90	$181.90
Purchase #2	$233.91	3.437%	$241.9495	$241.95	$241.95	$241.90
Purchase #3	$245.90	6.359%	$261.5368	$261.54	$261.55	$261.50
Purchase #4	$56.65	10.122%	$62.3841	$62.38	$62.40	$62.40
Purchase #5	$206.27	10.421%	$227.7654	$227.77	$227.75	$227.80
Purchase #6	$68.52	4.178%	$71.3828	$71.38	$71.40	$71.40
Purchase #7	$34.32	11.666%	$38.3238	$38.32	$38.30	$38.30
7 purchase totals =	$1,019.06		$1,085.2328	$1,085.23	$1,085.25	$1,085.20